Diemer



Jan. 31, 1956 G. DIEMER 2,733,305

ARRANGEMENT FOR AMPLIFYING CENTIMETRE WAVES Filed July 23,, 1949 INVENTOR. GESIN Us .DLEMEIZ.

AGENT United States Patent Hartford National Bank and Conn., as trustee Application July 23, 1949, Serial No. 106,452

Claims priority, application Netherlands September 30, 1948 2 Claims. (Cl. 179171) assignor to Trust Company, Hartford,

This invention relates to arrangements for amplifying centimetre waves, comprising a travelling wave tube, i. e. an electron tube in which an electron beam moves along the axis of a helix and interacts with an electromagnetic wave travelling along this helix in a manner such that the electron movement in the beam is substantially in phase with the travelling, electromagnetic wave. In such arrangements it is diflicult to fulfil the two requirements for a satisfactory amplification, viz. high amplification and high output. A high amplification requires a long helix. With a long helix however, the electrons can be delayed only slightly before getting out of phase with the electromagnetic wave travelling along the helix. In order to permit the extraction of high energy, the helix should therefore be short.

The invention has for its object to provide an improved arrangement, which produces both a high amplification and a satisfactory output.

According to the invention, an arrangement for amplifying centimetre waves, comprising an electron tube in which the electron beam moves along the axis of a helix and interacts with an electromagnetic wave travelling along the helix, is characterized in that the helix comprises two parts which are not coupled by an electron beam and of which the length of the first part is a comparatively great number of wave lengths and that of the second part a comparatively small number of wavelengths, such that the ratio between these numbers is at least 2, the smaller number being 15 at the most and the greater at least 30.

The first part of the helix owing to its length is adapted to provide a high amplification whereas the second part, as an amplifier, is capable of providing a high output. The output end of the first part and the input end of the second part of the helix may be coupled by direct connection or by a waveguide. The two parts of the helix may co-operate with the same electron beam, if coupling by the beam is avoided by providing damping means in the proximity of the beam between the two parts of the helix. Although satisfactory results are obtained with lengths of the helix parts equal to 30 and 15 wavelengths, materially improved results may be obtained if the length of the first part of the helix is at least 40 wavelengths and that on the second part is wavelengths at the most.

In order that the invention may be more clearly understood and readily carried into effect, it will now be described more fully with reference to two embodiments thereof illustrated in the accompanying drawing, in which Fig. 1 shows part of an arrangement comprising a travelling wave tube in which two separate helix parts are provided and Fig. 2 shows part of an arrangement according to the invention, in which the long part of the helix is provided in one travelling wave tube and the short part of the helix is provided in another travelling wave tube.

Referring now to Fig. 1, reference numeral 1 designates the glass wall of a tube, 2 a cathode and 3 an electrode for accelerating the electrons emanating from the cathode 2. Between-two annular electrodes 5, which are spaced apart by a distance of more than 35 cms., is provided one part- 6 of a helix having a diameter of 7 mms. and a .pitch' -of 2.5 mms. wound from molybdenum "wire of 0.5 mm. diameter. Between two annular electrodes 7, which are spaced apart about 15 cms., is provided a similar second part 8 of a molybdenum wire the helix of the same pitch and diameter as part 6 and wound from molybdenum wire of the same diameter. A collector electrode 4 is provided at the end of the tube 1 remote from the cathode 2. The first annular electrode 5 is surrounded by the end of a waveguide 9 and, similarly, the second electrode 7 is surrounded by a waveguide 10. The second annular electrode 5 and the first annular electrode 7 are coupled by a U-shaped waveguide 11. Between the two parts of the helix a layer of graphite 16 is provided on the tube 1, in order to prevent the electron beam from bringing about a coupling between the two parts of the helix. With a beam current of 10 mat. and a wavelength of 10 cms., the first part of the helix, the length of which is equal to about 30 wavelengths is capable of amplifying by a factor of about 100. If the annular electrodes and the helix are at a voltage of more than 2500 v., an energy of at least 5 w. is obtainable from the waveguide 10 at a wave length of 10 cms.

In Fig. 2, one part of the helix is contained in each of two tubes. The cathode of the second tube 12 is designated by 13, the accelerating electrode by 14 and the collector electrode by 15. Similar parts of Figures 1 and 2 are designated by the same reference numerals. The helix is again at a voltage of more than 2500 v.

What I claim is:

1. Apparatus for amplifying centimetre waves comprising first and second traveling wave tubes each including a helix and means to direct an electron beam along the axis of the helix, the helix in the first tube having a length corresponding to a relatively great number of wavelengths, the helix in the second tube having a length corresponding the helix in the second tube, means coupled to the input of the helix in the first tube for inserting an input signal thereat, and means coupled to the output of the helix in the second tube for deriving output signals therefrom corresponding to the input signal.

2. Apparatus for amplifying centimetre waves comprising first and second traveling wave tubes each including a helix, a pair of annular terminals connected to the ends of the helix, a collector electrode and means to direct an electron beam along the axis of the helix toward said electrode, the helix in the first tube having a length corresponding to a relatively great number of wavelengths, the helix in the second tube having a length corresponding to a relatively small number of Wavelengths, said numbers being at least in a two to one ratio, said greater number being at least 30 and said smaller number being at most 15, a first wave guide coupling the output terminal of the helix in the first tube with the input terminal of the helix in the second tube, a second wave guide coupled to the input of the helix in the first tube to insert an input signal thereat, and a third wave guide coupled to the output of the helix in the second tube to derive an output signal therefrom corresponding to the input signal.

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